1. Field of the Invention
The present invention relates generally to anatomical support apparatus, and more particularly to mattresses and seat cushions having at least one thermoplastic elastomeric honeycomb panel.
2. Description of the Prior Art
Substantially immobile people (i.e. wheelchair bound users) have a great need for support cushions that minimize the development of decubitus ulcers (i.e. bedsores) that can occur during long periods of confinements to beds or chairs.
Traditionally, foam and gel-filled materials have been used in seat cushions to absorb shock, reduce pressure, and provide support for wheel chair users. There are many prior art seat cushions that are comprised of a foam cushion encased within a washable covering, wherein the foam cushion is formed so as to provide a comfortable seating surface. For example, the foam cushion may have a cut-out or contact-free zone formed through it to reduce pressure on the user's spine, coccyx (i.e. tailbone), or ischial tuberosities, or to eliminate physical contact between the cushion and particularly sensitive portions of the user's body.
In other devices, the foam is specially tapered or shaped to enable the user to easily rise from the seat. Shaping the foam in such cushions helps reduce high pressure areas and positions the user for posturing, but only if the user's anatomy fits the contours of the shaped foam. High pressure points will still occur if the user has an anatomy that does not conform to the contours of the shaped foam. This is frequently the case when the user is an amputee, or is improperly positioned on the cushion, or is changing positions on the cushion.
In yet other prior art devices, a gel or other fluid-like substance fills an impermeable sack which is disposed within or on a foam envelope. The entire assembly is encased within a moisture resistant cloth, vinyl and/or urethane, or waterproof covering and placed on a seat as a seat cushion. In some cases the gel-filled cushion is formed with contours or contact-free zones to relieve contact and pressure on sensitive portions of the user's body. For example, U.S. Pat. No. 5,191,752 discloses a seat cushion formed from silicon dielectric gel is used in an equestrian saddle. The gel cushion, although somewhat shock absorbent, is heavy and prone to damage from punctures and the like. In U.S. Pat. No. 5,201,780 a tri-layered mattress pad is disclosed. The pad includes a cover or casing containing an interior strata of a plastic film layer atop a fluid bladder layer supported on a foam layer. The pad is designed to reduce the development of bedsores by reducing normal and lateral pressures and forces on the bed user. As discussed below, there are disadvantages associated with foam and gel-filled materials.
One problem associated with gel materials is that they retain heat. During periods of continuous contact with a user's body, the temperature and moisture in the contact areas between the gel-filled cushion and the user's body also increases. An elevated gel material temperature causes user discomfort and exacerbates any existing injuries (e.g. bedsores) the user may have. The moisture increase also creates an unsanitary condition for the user because bacterial growth in the contact area is promoted and the user's injuries are likely to become infected.
Secondly, gel-filled cushions disposed in the wheelchairs of athletic users are especially uncomfortable. During outdoor athletic activity (i.e. during exposure to sunlight) or during periods of physical exercise, the temperature of the gel material reaches and remains at high levels. The gel material remains hot even when the user stops exercising and is attempting to cool down. Also, in cold weather, the gel freezes into a solid or semi-solid state.
In a gel-filled cushion, the gel tends to move (i.e. spread) away from the area under load. The user of the cushion, or his assistant, is required to "knead" (i.e. push) the gel back into the proper location beneath the user's body. This is a tiring, difficult, and inconvenient activity.
Another shortcoming of using gel-filled cushions is that the impermeable sack which contains the gel can have a hammocking effect on the user's prominences. This causes high pressure zones beneath the protruding areas resulting in sores or other injury.
Finally, gel-filled cushions are relatively heavy, and especially vulnerable to damage or destruction from puncturing.
In addition, there are shortcomings associated with foam materials which, for example, are susceptible to taking a compression set after many periods of use. It is typical, that after a prolonged period of use the foam cells collapse and the support benefit of the cushion is lost. Also, foams cushions must be encased within impermeable coverings because they readily absorb fluids. The foam cushion must be replaced if incontinence or an accidental spill wets a cushion with a torn covering.
Some wheelchair cushions utilize pneumatic devices as a pressure relieving system for reducing ischemic injury. U.S. Pat. No. 5,193,237, for example, discloses a pneumatic wheelchair cushion having a number of separate unattached air sacks arranged in a matrix. Reduced airflow and therefore reduced air pressure is periodically provided within the cushion so that each air sack will have reduced pressure for a predetermined period of time. A self-regulating air distribution is provided such that when the occupant shifts his/her weight so as to overcome the air pressure in a sack, the system automatically backflows air into that particular sack thereby cushioning the user.
The disclosed wheelchair device is complex, and requires electrical power and pressurized air. Such devices are overly complicated, costly to acquire, and costly to maintain. Also, the air cushion device must be frequently adjusted, can be punctured, and is unstable for a user.
In addition, there are some prior art mattresses that include a matrix of air cells that are inflated and deflated to more evenly support bodies and reduce the development of bedsores. In addition to the air supply components (e.g. compressor, valving, tubing, etc.) these mattresses also require a computer to constantly measure the resistance in each air cell and to control the reaction of each cell to pressure and load changes by varying the deflation and inflation in each cell. These devices are also costly, complicated, require adjustment, and subject to puncture damage.
The prior art also discloses resilient honeycomb structures used in personal-use items. U.S. Pat. Nos. 5,134,790 and 4,485,568 disclose using resilient honeycomb structures in the sole of shoes. Also, U.S. Pat. No. 4,422,183 to Landi et al. discloses a protective body shield having a honeycomb structure constructed from a resilient flexible material. Finally, U.S. Pat. No. 5,203,607 discloses an improved bicycle seat including a rigid shell supporting a foam layer having a pad of thermoplastic elastomer honeycomb disposed within or thereon. In all of these devices, the honeycomb structures are not utilized in seat cushions and mattresses.
Thus, there is a need to provide an improved anatomical support apparatus that maximizes pressure relief, stability, comfort, durability, maintainability, and weight, yet does not possess the short-comings of the presently employed devices.